Biomedical subjects
D C Sabiston
Publications and source records attributed to D C Sabiston.
Angiographic evaluation of chronic pulmonary embolism.
In some patients acute pulmonary emboli may fail to resolve normally, resulting in chronic pulmonary embolism. This may lead to pulmonary hypertension, respiratory insufficiency, cor pulmonale, and death. The angiographic evaluation in nine patients with chronic pulmonary embolism who underwent embolectomy is presented. Particular emphasis on the predictive value of selective bronchial arteriography in four of these patients is considered. In chronic pulmonary embolism, pulmonary arteries distal to obstructed areas may remain patent and be supplied by hypertrophied bronchial arteries. Since back-bleeding of arterial blood from the bronchial circulation at surgery may predict the success of embolectomy, preoperative bronchial arteriography may be useful for predicting potential surgical success.
Comparison of electrocardiographic and left ventricular functional changes during exercise.
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Noninvasive assessment of the effects of aorta-coronary bypass grafting on ventricular function during rest and exercise.
Ventricular function was measured by radionuclide angiocardiography during rest and exercise in patients before and approximately 4 months after aorta-coronary bypass grafting. The first group of seven patients continued to have symptomatic chest pain after operation. The second group of 13 patients were asymptomatic after operation but, since they had been studied before operation, consented to postoperative study. Before operation, both patient groups demonstrated similar degrees of myocardial ischemia during exercise as documented by a decrease in ejection fraction, by large increases in end-diastolic and end-systolic volumes, and by exercise-induced wall motion abnormalities. After aorta-coronary bypass grafting, ventricular function in the symptomatic patients was unchanged during rest and exercise. In contrast, ventricular function during rest and exercise in the asymptomatic patients was markedly improved. With exercise, the ejection fraction increased and the exercise-induced wall motion abnormalities seen before operation were abolished. Therefore, aorta-coronary bypass grafting can effectively reverse exercise-induced left ventricular dysfunction in patients with coronary disease. Moreover, the change in left ventricular function demonstrated by radionuclide angiocardiography correlated with the clinical status of the patient groups.
Surgical management of aortic abdominal aneurysms in patients with severe pulmonary insufficiency.
In view of the poor prognosis associated with the natural history of aortic abdominal aneurysms, this disorder is being surgically corrected in an increasing number of patients. There remains a group of patients with serious coexisting disease in whom careful consideration must be given concerning the risk of operation. One such group of patients is those with severe respiratory insufficiency. The records of ten patients with clinical and physiologic evidence of severe pulmonary insufficiency and concomitant aortic abdominal aneurysms were reviewed. While some patients were refused operation for severe cardiovascular disease, malignant disease and obesity, none was denied operation on the basis of severe respiratory insufficiency alone. With detailed respiratory assessment, appropriate preoperative preparation and careful attention to pulmonary function in the postoperative course, these patients can now undergo aortic abdominal aneurysm resection and grafting with a high expectation of success. In the ten patients, no operative deaths occurred, and all were discharged from the hospital having undergone a favorable postoperative course.
Measurement of global ventricular function in patients during cardiac operations using sonomicrometry.
In these studies, we evaluated the applicability of pulse-transit sonomicrometry for measuring changes in global cardiac activity in patients during cardiac operative procedures. In six patients two epicardial ultrasonic crystals (8 mm) were sutured across the left ventricular minor axis. Diastolic pressure-length data were recorded as left ventricles were filled passively to transmural pressures (P) from 0 to 20 mm Hg. Data were collected at the beginning of cardiopulmonary bypass and again 15 minutes following periods of induced global ischemia (29.8 +/- 0.8 minutes). Minor axis length data were normalized to Lagrangian strain (epsilon), and best-fit regression curves were obtained from P-epsilon by computer analysis. Nonlinear elastic constants, alpha and beta, were mathematically derived as additional curve descriptors. Decreases in ventricular compliance were demonstrated as leftward shifts in both computed and measured P-epsilon curves. Global ischemia appeared to effect a decrease in overall ventricular diastolic compliance in all patients studied (p =7E 0.01 at 5, 10, 15, 20 mm Hg). Simultaneously, no statistical change occurred in lo (62.93 +/- 2.80 mm), which represented end-diastolic length (EDL) at 0 mm Hg transmural pressure. Following coronary grafting several patients showed augmented systolic excursion when compared at similar EDL. For those analyses, shortening was compared at specific minor axis EDLs rather than filling pressures. These data indicate that experimentally developed sonomicrometry may safely provide accurate indices of systolic and diastolic ventricular properties during operations necessitating cardiopulmonary bypass. Thus various cardioplegic solutions, ischemic arrest periods, and inotropic agents may be evaluated more objectively.
Pathophysiology, diagnosis, and management of pulmonary embolism.
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An experimental model of pulmonary embolism.
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Effect of increases in afterload before and after coronary occlusion in awake dogs.
Ventricular function curves relating stroke work and left ventricular end-diastolic pressure were generated in awake dogs during increases in preload produced by infusion of fluid and during increases in afterload produced by administration of phenylephrine. The ventricular function curves produced by preloading were steeply upsloping whereas those produced by afterloading were essentially horizontal. Coronary occlusion produced downward displacement of these horizontal curves, but no change in slope. This increases in afterload did not help to demonstrate the functional impairment produced by coronary occlusion.
The effects of hypothermia on myocardial oxygen consumption and transmural coronary blood flow in the potassium-arrested heart.
Hypothermia remains the primary adjunct employed to lower cellular metabolism during various cardiac procedures. In these experiments, left ventricular myocardial oxygen consumption (MVO2) and transmural blood flow (TBF) were measured during cardiopulmonary bypass with the range of temperatures used clinically. Determinations were made in empty beating normothermic hearts and after potassium cardioplegia at 37, 32, 28, 22, 18, and 15 degrees (K+ = 15--37 meq/L: Hct 25 volumes %). Oxygen content of the total coronary sinus collection was compared with a large volume arterial sample using a Lex-O2-Con-TL analyzer (vs Van Slyke, R = 0.98). Transmural blood flow was measured at each temperature using microspheres (8 microns), and perfusion was maintained at 80 mmHg. Asystole (37 degrees) alone decreased MVO2 from 5.18 +/- 0.55 to 1.85 +/- 0.20 ml O2/min/100 g of left ventricle or approximately 65% (p less than 0.001). With progressive cooling to 15 degrees an additional 82% decrement in oxygen uptake occurred during asystole (p less than 0.001). During asystole at 37 degrees the decrease in MVO2 was reflected mainly by a large decrement (p less than 0.01) in TBF (1.27 +/- 0.19 to 0.74 +/- 0.17 ml/min/g of mean left ventricular flow). However, with cooling below 32 degrees, the arteriovenous oxygen difference narrowed progressively (p less than 0.001) while TBF paradoxically returned to control levels. Endocardial/epicardial flow ratios were not altered by cooling. These data not only confirm earlier reports describing a sequential drop in MVO2 with incremental myocardial cooling, but also establish MVO2 levels for perfused hearts arrested by potassium at lower temperatures (18--15 degrees). Moreover, as transmural blood flow becomes independent of metabolic necessity during hypothermia, coronary autoregulation appears to be impaired, possibly affecting detrimental tissue over perfusion.
Response of the secretory immune system to bronchogenic carcinoma of the lung.
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Intraoperative relationships between regional myocardial distribution of bypass graft flow and the coronary collateral circulation.
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Alexis Carrel, 1912--Nobel Prize.
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Prophylaxis of thromboembolism.
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Noninvasive assessment of hemodynamic effects of mitral valve commissurotomy during rest and exercise in patients with mitral stenosis.
Noninvasive radionuclide angiocardiography (RNA) provides simple and accurate assessment of parameters of cardiac function during rest and during maximal exercise. Left ventricular function was assessed by RNA in nine patients with isolated mitral stenosis before and approximately 6 months after mitral commissurotomy. Before operation, the mean mitral valve gradient was 14.0 +/- 2.8 mm Hg, and the mean mitral valve area was 1.20 +/- 0.3 cm2. Each patient was evaluated at rest and during maximal exercise on an isokinetic bicycle ergometer before and after commissurotomy. Heart rate, ejection fraction, end-diastolic volume, stroke volume, pulmonary transit time, cardiac output, and diastolic ventricular filling rate were determined by the radionuclide technique. Before operation, patients with mitral stenosis had characteristic changes from rest to exercise which supported restriction to diastolic ventricular filling as the primary limitation in generating a cardiac output during exercise. The stroke volume was unchanged from rest to exercise. Thus the cardiac output during exercise was heart rate dependent. However, after commissurotomy the stroke volume increased from rest to exercise. Therefore, cardiac output during exercise was achieved by heart rate and an augmented stroke volume. Moreover, the pulmonary transit time was reduced during rest and exercise after operation. The maximum ventricular ejection and filling rates were markedly increased during rest and exercise after commissurotomy. These differences in hemodynamic parameters at rest and during exercise document the mechanics of increased exercise tolerance in patients with mitral stenosis after mitral commissurotomy.
Assessment of ventricular diastolic properties and systolic function in man with sonomicrometry.
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Noninvasive radionuclide assessment of cardiac function in patients with peripheral vascular disease.
Disorders of the peripheral vascular system often are associated with heart disease which may increase operative risk. The purpose of this study was to investigate the clinical usefulness of radionuclide angiocardiography for evaluation of cardiac function in patients with vascular disorders. This simple procedure provides measurements of cardiac output, pulmonary blood volume, and left ventricular end-diastolic volume, stroke volume, and ejection fraction with no significant risk or discomfort to the patient. A total of 22 patients with vascular disorders were studied by this technique. Five patients had systemic arteriovenous malformations. The cardiac output, end-diastolic volume, and stroke volume were documented to be greater than normal in these patients before operation. In three patients studied following closure of the arteriovenous fistula, the cardiac output, left ventricular end-diastolic volume, and stroke volume decreased. Postoperative changes in left ventricular ejection fraction were variable. A group of 17 patients with atherosclerotic vascular disease underwent cardiac evaluation. In nine patients with no history of cardiac disease, the lowest ejection fraction of 0.45 occurred in a patient with a saccular thoracic aneurysm, the only patient of the 22 who died after operation. A wide variation in ejection fraction was observed in patients with a history of cardiac disease which ranged from 0.32 to 0.86. Objective documentation of cardiac function by radionuclide angiocardiography would appear to enhance the management of patients with peripheral vascular disorders.